Biphasic inks

Biphasic inks contain both attractive particles and repulsive particles in a carrier liquid (89). The attractive colloidal particles attract one another, thus forming a gel phase. In contrast, the repulsive colloidal particles do not attract each other, thereby remaining as a fluid. 

The inclusion of both types of coUoidal particles produces structures with feature sizes as small as 10 pm. Thus, biphasic inks can be used to produce three-dimensional patterned structures with feature sizes smaller than 50 pm. 

It is believed that these properties are due to the presence of the repulsive particles, which increase the colloid volume fraction but do not participate in the formation of a gel. 

Hydrophobic coUoids/hydrophiUc colloids biphasic inks, 

Biphasic inks with attractive and repulsive dispersants. 

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In a first representative t5q)e of biphasic inks, the attractive particles are hydrophobic colloids, the repulsive particles are hydrophilic colloids and the carrier liquid is hydrophobic. More genericaUy, depending on the choice of carrier liquid, a first colloid with a high interfacial energy with the carrier Hquid will yield attractive particles, whereas a second colloid with a low interfacial energy with the carrier liquid will give rise to repulsive particles. Thus, mixing the two colloids and the carrier liquid will yield a biphasic ink. If desired, a carrier liquid whose hydrophobicity is dependent on the temperature or other variables may be chosen. The relative hydrophobicity of the particles may also vary with the temperature or other variables. 

In a second representative type of biphasic inks, the attractive and repulsive particle may be created by using a first set of particles and a second set of particles differing in their isoelectric point. When the composition is at the isoelectric point of the first set of particles, the first set will tend to attract one another. At the same time, the second set will be highly charged and repulsive. Accordingly, a combination of the first set and the second set of particles will provide a biphasic ink. For example, a combination of any two of the following colloids, at a pH where one of the types of particles is... 

In 2002 BASF established the first dedicated industrial-scale ionic liquid-based process [7]. The so-called BASIL process (BASIL = Biphasic Acid Scavenging utilizing Ionic Liquids) is used for the synthesis of alkoxyphenylphosphines, which are important raw materials in the production of BASF s Lucirines (Scheme 9-3), substances that are used as photoinitiators to cure coatings and printing inks by exposure to UV light. 

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